Dosing dispensers for the addition of laundering and softening materials during the washing and rinsing cycles in an automatic washing machine are well known in the art.
Dispensers for adding materials during the rinse cycle in an automatic washer are generally more complex than those employed for adding materials during the wash cycle due to the fact that the rinse additive dispenser is normally inserted when the wash cycle begins and must survive the entire wash cycle without dispensing the material contained inside, yet reliably open during the spin cycle at the conclusion of the wash cycle to deliver the rinse water additive at a point in time which will be effective.
One early prior art example of a centrifugal dispenser for delivering materials such as softeners and bleaches is disclosed in U.S. Pat. No. 2,956,709 issued to Nison et al. on Oct. 18, 1960.
Another prior art example of a centrifugal dispenser which is specifically intended to introduce a rinse water additive is disclosed in commonly assigned U.S. Pat. No. 3,888,391 issued to Merz on Jun. 10, 1975 and hereby incorporated herein by reference.
Still another example of such a prior art rinse water additive dispenser is disclosed in U.S. Defensive Publication No. T993,001 to McCarthy, which was published on Apr. 1, 1980, and which is hereby incorporated herein by reference.
Dispensers of the type disclosed in the Merz Patent and the McCarthy Defensive Publication employ a valve means which is automatically opened by centrifugal force acting upon a counterweight during the spin cycle at the conclusion of the wash operation. After the spin cycle, dispensers of this type fall from the wall of the washing machine drum and rinse water floods the dispenser, mixing with and dispensing the additive into the rinse water.
While dispensers of the aforementioned type have functioned adequately for their intended purpose with prior art rinse water additives, recent trends in the development of more effective rinse water additives have been in the direction of more highly concentrated products which deliver comparable performance benefits to the less concentrated products which they are intending to replace. For example, one fluid ounce of a highly concentrated fabric softener, such as Ultra Downy.RTM. now being marketed by The Procter & Gamble Company of Cincinnati, Ohio, can deliver benefits comparable to three fluid ounces of a less concentrated fluid softener product of the type which has been on the market for several years.
However, to obtain maximum performance benefits from the newer more highly concentrated products, it has become much more critical that substantially all of the additive material initially placed in the dispenser be retained within the dispenser during the wash cycle, since any lost additive material will not be available to accomplish its intended objective during the rinse cycle.
It has been observed that prior art dispensers of the type described earlier herein may tend to lose some of the additive initially placed in the dispenser during the wash cycle due to flexing of the valve member during the wash cycle, even though the valve may remain in a substantially closed position until the dispenser is subjected to a spin cycle. This premature loss of product due to leakage negatively impacts the benefits provided by highly concentrated rinse additives, since this loss of additive material during the wash cycle renders it unavailable to impart benefits to the laundered fabrics during the rinse cycle. Loss of a highly concentrated additive is particularly detrimental, since it results in a greater loss of the active materials when compared to less concentrated fluid product forms of the prior art.
An automatic dosing dispenser of the type disclosed in copending, commonly assigned U.S. patent application Ser. No. 07/851,581, filed on Mar. 16, 1992 in the names of Richard M. Baginski, Jerome P. Cappell and Gary E. McKibben, the disclosure of which is hereby incorporated herein by reference, discloses a substantially improved valve means employing a movable piston type seal which maintains a more effective seal between the interior of the dispenser and the atmosphere until such time as the dispenser is opened by the centrifugal forces acting upon the counterweight during the spin cycle of the washing machine.
While the improved valve design of Baginski et al. has proven effective in helping to establish a seal which resists premature loss of the liquid laundry additive prior to automatic opening of the valve during the spin cycle, it has unexpectedly been discovered that maintaining such a seal throughout the wash cycle can introduce problems which were not presented when prior art automatic dosing dispenser valves which tended to leak, and consequently which failed to establish an effective seal to the atmosphere, are employed. Specifically, it has been observed that when an automatic dosing dispenser having a valve of the type disclosed by Baginski et al, which establishes an effective seal to the atmosphere, is immersed in a hot wash a pressure buildup occurs within the dispenser. In the case of a hot water wash, the internal pressure acts against the opening motion of the valve during the spin cycle, thereby tending to prevent the valve on the automatic dosing dispenser from reliably opening during the spin cycle. Because the automatic dosing dispenser has two opportunities to open during most complete washing machine cycles, this unreliability may result in the dispenser failing to open during either spin cycle or, even more undesirably, it may open during the second spin cycle used to remove the rinse water from the washing machine. At this point the additive will be of no value. What's more, it may cause staining or discoloration of the fully laundered articles.
Conversely, if a vacuum is formed inside the dispenser during a cold water wash cycle, the pressure imbalance created with respect to the atmosphere tends to cause premature opening of the valve, perhaps losing all of the laundry additive during the wash cycle and rendering it totally unavailable during the desirable portion of the rinse cycle.